Because of the extensive use and statistical certainty of damage through accident, abuse or the like, a railroad or any other company that owns and operates boxcars must contend with the problem of repairing and replacing rolling type boxcar doors. As the boxcars become disabled, it is very important to be able to repair or replace the door promptly so that boxcars do not remain idle any more than necessary. A boxcar represents a substantial capital investment which is not producing income if it is "off line" awaiting repairs or the availability of a replacement door. All companies strive to make maximum use of their capital investment and it makes no economic sense for a boxcar to be idle for lack of a part representing only a fraction of the total investment.
Unfortunately, the boxcar door industry has developed over the years with the various manufacturers supplying different sizes of rolling type boxcar doors so that no industry standard for size has been set. Also, because boxcar manufacturers generally supply boxcars according to their own standard specifications, specifications for door openings have continually changed over the years, so that users of railroad boxcars have accumulated an inventory of boxcars having door openings and doors with widely varying dimensions. For example, one railroad has an inventory of approximately 14,000 boxcars with 37 different sizes of door openings and doors. As is apparent, this failure to set industry standards and lack of coordination and continuity between the boxcar and door manufacturers has created a maintenance nightmare for boxcar users. Because of the variety of door sizes, a substantial capital investment is required to carry an inventory sufficiently varied to ensure that the right size doors are available. This greatly increases the amount of inventory investment required for replacement doors and also increases the possibility that the right size boxcar door is not available to make a needed repair or replacement.
The type of car which is involved in an accident or deteriorates sufficiently to require repair can only be statistically predicted and a door inventory must be selected and maintained from this prediction. However, a shortage of doors often develops because of the widely varying dimensions of the doors, the relatively few number of door manufacturers, and the long delivery times. It must be remembered that boxcar doors are quite large and heavy, being constructed of steel castings and plating which generally take a significant amount of manufacturing and assembly time. Thus, door manufacturers generally quote extended delivery times of 6 months or more. An inventory "prediction" must therefore account for 6 months of accidents, which is virtually impossible. As a result, extensive repairs are made to doors that would otherwise be considered scrap, and other boxcars must be held out of service until the specific door required can be ordered and received, all at great expense and waste of capital investment.
Another maintenance problem which exacerbates those mentioned above concerns the roller mechanism for the roller type door. Generally, in the prior art, a single roller with a fixed axle is provided at each end of the door. A rail is secured to the side of the car door and the door rolls along the rail to move between its open and closed positions. Thus, the full weight of the door must be supported from these two rollers having fixed axles although the weight of the doors may be quite substantial, approaching 1000 pounds. Because of the abuse and damage received during usage, it becomes very likely for either the door track to develop kinks or the rollers to become jammed or otherwise damaged such that the door becomes inoperable or only operable with great difficulty. To maintain a car in service, a badly operated door may be ignored which presents a safety hazard to the men opening and closing these doors. This also reduces the effectiveness of the boxcar as power equipment may be required to operate these doors. Thus, the failure of the roller mechanism and the door track contributes to the failure rate of boxcar doors and increases the maintenance problems associated therewith.
To solve these problems applicants have designed and built a rolling type boxcar door which provides an adjustable height and width as well as an improved traverse mechanism utilizing a pair of pivotally mounted, double-wheeled bogeys. Special attention has been given to developing a universal door having an improved and easily replaceable traverse mechanism by providing an adjustable panel at the lower end of the door which also serves as the mounting position for the double roller bogeys. The adjustable lower panel is slidably retained at the lower edge of the door between a pair of side frames, one mounted to each side of the main door panel. A stop block mounted to the inside of each side frame slidably captures the adjustable panel and allows it to be telescoped with the main door panel to adjust the overall door height. The adjustable panel is welded in place at the proper height, but can be cut free later, as desired. Thus, the entire traverse mechanism can be replaced by replacing the adjustable panel.
The width of the door may be also adjusted by changing the mounting position of a vertically mounted spark strip. As is known in the art, the spark strip on the car door interlocks with a spark strip on the side of the boxcar to achieve a seal at the door edge. Of course, a seal at the other edge of the door is provided by the edge of the door engaging the frame or another car door.
A significant advantage of applicant' new door design is that it drastically reduces the amount of inventory of doors which must be maintained to service a large number of boxcars. For example, applicants have found that eight basic door sizes having the adjustable panel feature can replace thirty-seven different doors from various manufacturers. Thus, an inventory of less than one-fifth (1/5) the number of doors previously required can be carried to support the same number of boxcars. The versatility of applicant' door also reduces the possibility of an out-of-stock condition on any one size as a greater number of each kind of door may be carried in stock for the same investment. It is further anticipated that the cost of the doors may be significantly reduced as applicants' adjustable door requires no castings and may be manufactured on a production line basis whereas custom built doors as in the prior art utilize castings and must be produced on an order by order basis.
Applicants' improved traverse mechanism has special advantages over the prior art which helps to minimize the door maintenance problem. With the prior art designs, proper door operation depended on a straight and level track and the smooth rolling of a pair of fixed axle traverse wheels. Any damage or failure of either the track or a traverse wheel greatly increased the force required to operate the door. Furthermore, even when newly installed, the fixed axle traverse wheels require a significant force to be operated merely because of the manufacturing tolerances in both the door and the track. However, applicants' double roller bogeys significantly reduce the amount of force required so that a man may move what may be a 1,000 pound door with the force of his arm only. This is achieved by a pair of pivotally mounted double roller bogeys which "step" up and over any kinks or obstructions in the door track. Thus, it is no longer necessary for the door track to remain absolutely straight and level to ensure easy opening and closing of the door. Furthermore, by mounting the bogeys in the adjustable panel, should the traverse mechanism fail or be damaged, it may be easily replaced along with the adjustable panel. This greatly reduces the time required to repair a door, and also saves the replacement of the entire door as prior art doors are often scrapped for failure of the traverse mechanism.